If easy-off doesn't work for some reason then I would carefully wipe the painted letters with acetone. Just about anything is better than sanding.
I used Goof off and a 600 grit equal plastic steel wool equal. No issues overall. I preferred to use the spray vs the liquid onto a rag, wipe and rub with the wool.
Easy-Off Oven Cleaner works better and has a much lower chance of damaging the underlying gelcoat.Looks like Ill have to try your method. Easy-Off got the black trim around the blue lettering off, but it didnt seem to touch the blue lettering...The blue lettering is paint and not decal and on very thick & STUBBORN..
Acetone WILL work, I've done it myself on my own boat's painted on lettering. Try again with a little more elbow grease before resorting to sanding.